Valorization of pickled cabbage waste as a novel pectin source: Optimization, characterization

Recovery of food ingredients from agro-industrial by-products has become increasingly essential for sustainable food production through energy saving and lessening the carbon footprint. Pickled white cabbage production generates high amounts of pickled cabbage waste that contain valuable goods such as pectin. This study aimed to evaluate the valorization of pectin from pickled cabbage waste by comparing the conventional (CE) and ultrasound-assisted extraction (UAE). The UAE provided 2.14 times higher pectin yield (30.32%) compared to CE (14.14%) while reducing energy consumption and carbon dioxide emission (~ 7 times lower). Pectins obtained from conventional extraction (CEP) and ultrasound-assisted extraction (UEP) had high amounts of galacturonic acid (85.06 ± 1.76%, 87.95 ± 6.99%, respectively) and low degree of esterification (17.08 ± 1.14%, 14.71 ± 0.00%). The monosaccharide compositions of pectin were similar for CEP and UEP, comprising of galacturonic acid, glucose, arabinose, rhamnose and xylose. FT-IR, NMR and SEM confirmed the structural characteristics of pectins, and the effect of ultrasonication. Furthermore, UEP presented superior technological characteristics including water holding capacity (5.29 ± 0.38 g water/g pectin), oil holding capacity (1.58 ± 0.11 g oil/g pectin), emulsion activity (43.61 ± 1.12%) and emulsion stability compared to CEP. These findings show that pickled cabbage waste is a valuable source of low-methoxyl pectins and UAE is a promising extraction method for obtaining high amount of pectin along with reduced processing time and energy consumption. The UAE method using of citric acid instead of hazardous acids also offers environment-friendly method for pectin extraction.